1. Field of the Invention
The present invention relates to a fuel injection apparatus for an outboard machine in which a fuel within a fuel tank arranged at a position apart from an engine is supplied into a vapor separator by increasing a pressure to a low pressure by means of a low pressure fuel pump, the fuel is controlled to form a fixed liquid surface within the vapor separator by a fixed liquid surface control mechanism so as to be separated into vapor and liquid, a pressure of the fuel within the vapor separator is increased to a high pressure by a high pressure fuel pump so that the fuel is supplied toward a fuel injection valve attached to a fuel distributing pipe, and a high pressure fuel is injected and supplied into an intake pipe connected to the engine via the fuel injection valve controlled by an ECU, and in particular, relates to a vapor separator provided with a high pressure fuel pump.
2. Description of the Conventional Art
The conventional vapor separator provided with the high pressure fuel pump is shown in Japanese Unexamined Patent Publication No. 8-312485. A description will be given with reference to FIG. 3 (corresponding to a structure shown in FIGS. 22 and 23 in Japanese Unexamined Patent Publication No. 8-312485). Reference symbol V denotes a vapor separator, within which a fixed liquid surface control mechanism F is arranged. The fixed liquid surface control mechanism F is constituted of a valve seat 21 connected to a low pressure fuel flow passage 20, a float valve 22 opening and closing the valve seat 21 and a float 25 rotatably supported by a shaft 23 and in which an arm 24 is arranged so as to face to and contact with the float valve 22. In a low liquid surface state in which a fixed liquid surface X-X having a fixed height is not formed within the vapor separator V, the float 25 rotates in a counterclockwise direction, the float valve 22 opens the valve seat 21 and a low pressure fuel is supplied into the vapor separator V from the low pressure fuel flow passage 20. On the other hand, in a state in which the fixed liquid surface X-X is formed within the vapor separator V, the float 25 rotates in a clockwise direction, and the float valve 22 closes the valve seat 21 so as to stop the fuel supply from the low pressure fuel flow passage 20 into the vapor separator V, thereby forming and holding the fixed liquid surface X-X within the vapor separator V. As a high pressure fuel pump PH, a wesco type pump is used. A fuel suction passage PA of the high pressure fuel pump PH is inserted and arranged within a second fuel storage 26 separated from the vapor separator V via a filter 27. The second fuel storage 26 is held to be airtight by a seal ring 28 arranged in an upper portion thereof, and a lower portion thereof is communicated with the fixed liquid surface X-X of the vapor separator V by a communication passage 29. The vapor separator V provided with the high pressure fuel pump PH mentioned above is structured by respective elements being connected as shown in FIG. 2 and the fuel injection apparatus of the outboard machine is thereby formed. A description will be given with reference to FIG. 2. Reference symbol T denotes a fuel tank arranged at a position apart from the engine, the pressure of the fuel within the fuel tank T is increased to a low pressure by a low pressure fuel pump PC such as a diaphragm pump or the like, and the fuel having the low pressure is supplied toward the valve seat 21 of the vapor separator V via the low pressure fuel flow passage 20. The low pressure fuel is supplied into the vapor separator V via the valve seat 21, and a fixed liquid surface X-X is formed and held in the inner portion by the fixed liquid surface control mechanism F. The fuel stored within the vapor separator V is supplied into the second fuel storage 26 via the communication passage 29, the fuel stored within the second fuel storage 26 is sucked into the high pressure fuel pump PH via the filter 27 and the fuel suction passage PA, the pressure thereof is increased to a high pressure in the pump portion, and the fuel having the high pressure is supplied into a fuel distribution pipe D via a fuel discharge passage PB and a high pressure fuel flow passage 30. A part of the high pressure fuel supplied into the fuel distribution pipe D is circulated into the vapor separator V via a return fuel passage 31, and a fuel pressure within the fuel distribution pipe D is controlled to a predetermined fixed fuel pressure in accordance with a regulating effect of a pressure regulator R arranged within the return fuel passage 31. Further, the fuel having the predetermined pressure is injected and supplied into an intake pipe K connected to the engine E via the fuel injection valve J.
In accordance with the conventional vapor separator provided with the high pressure fuel pump mentioned above, it is hard to continuously supply a stable and accurate fuel into the intake pipe K from the fuel injection valve J, and a good operation of the engine is impeded. That is, a wesco type pump is frequently used as the high pressure fuel pump PH since a discharge pulsation is a little and a compact and light structure can be achieved. The wesco type pump is structured, as shown in FIG. 3, such that an impeller PD driven by a motor M is rotatably arranged within a pump chamber PC, and when a rotational force is transmitted to the impeller PD due to a rotation of the motor M, a pressure difference is generated between the front and the rear of a vane groove formed on an outer periphery of the impeller PD on the basis of a liquid friction, the pressure of the fuel within the pump chamber PC is increased by the repetition of the above operation in a multiplicity of vane grooves, and the high pressure fuel having thus the increased pressure is discharged out via the fuel discharge passage PB. On the other hand, on the basis of a rotation of the impeller PD within the pump chamber PC, the fuel pressure within the pump chamber PC is reduced, whereby bubbles are generated, and the bubbles are discharged out of the pump chamber PC via a vapor discharge port PE pierced so as to open toward a bottom portion of a cover from the pump chamber PC. If the vapor stays within the pump chamber PC without being discharged, the bubbles gradually accumulate to become bigger, and a vapor lock is generated and the pump operation is impeded. Further, the bubbles containing the fuel discharged from the vapor discharge port PE is discharged into the second fuel storage 26, the upper opening of the second fuel storage 26 is sealed with a sealing 28 at this time, and the bubbles stay within the second fuel storage 26 because the second fuel storage 26 is in a closed state. Further, when a fixed amount of the bubbles stay, the bubbles are sucked into the pump chamber PC via the filter 27. In accordance with the structure mentioned above, the bubbles are contained in the fuel discharged from the high pressure fuel pump PH, and when the fuel containing the bubbles is injected from the fuel injection valve, an amount of injection from the fuel injection valve J is reduced in correspondence to the bubbles, so that it is impossible to supply an accurate fuel from the fuel injection valve J. Further, since the bubbles are contained in the fuel, the fuel supply is intermittently carried out, so that in any cases, an operability of the engine is deteriorated. Further, in the case that a large amount of bubbles stay within the pump chamber PC, there is a risk that the pump operation by the impeller can not be executed.
Further, paying attention to the vapor separator, a return fuel drops and flows into the vapor separator V via the return fuel passage 31 while the low pressure fuel drops and flows into the vapor separator V via the valve seat 21. Accordingly, since the bubbles are sucked into the fuel stored within the vapor separator V, the bubbles scatter in the fuel within the vapor separator V. Further, a part of the bubbles flow into the second fuel storage 26 via the communication passage 29. In accordance with the structure mentioned above, there is generated the same problem in the second fuel storage 26 as that generated by the bubbles discharged within the second fuel storage 26 from the vapor discharge port PE.
A vapor separator in an outboard machine in accordance with the present invention is made by taking the problems mentioned above into consideration, and an object of the present invention is to provide a vapor separator in an outboard machine in which a high pressure fuel pump is arranged in an outer portion of a vapor separator, wherein the high pressure fuel pump does not suck bubbles discharged from the high pressure fuel pump and bubbles generated within the vapor separator and it is possible to continuously supply a stable fuel from a fuel injection valve toward an engine, and another object thereof is to prevent a discharge performance of the high pressure fuel pump used in the vapor separator from being reduced.
In accordance with a first aspect of the present invention, in order to achieve the objects mentioned above, there is provided a vapor separator in an outboard machine in which a fuel within a fuel tank arranged at a position apart from an engine is supplied into a vapor separator by increasing a pressure by means of a low pressure fuel pump, and a pressure of the fuel within the vapor separator controlled to form a fixed liquid surface by a fixed liquid surface control mechanism is increased by a high pressure fuel pump so that the fuel is injected and supplied into an intake pipe connected to the engine via the fuel injection valve, characterized in that a filter is arranged in a bottom portion of a fuel pump receiving case, an upstream chamber of the filter is connected to a portion below the fixed liquid surface of the vapor separator via a fuel inflow passage, a fuel inflow passage of the high pressure fuel pump received and arranged within the fuel pump receiving case is connected to and arranged in a downstream chamber of the filter, a vapor discharge chamber separated from the downstream chamber of the filter and facing to a vapor discharge port of the high pressure fuel pump is provided in a bottom portion of the high pressure fuel pump within the fuel pump receiving case, the vapor discharge chamber is communicated with an annular chamber formed between an outer periphery of the high pressure fuel pump and an inner periphery of the fuel pump receiving case, and the annular chamber is communicated with a portion below and close to the fixed liquid surface of the vapor separator via the vapor discharge passage.
Further, in accordance with a second aspect of the present invention, in addition to the first aspect mentioned above, the vapor separator is characterized in that the upstream chamber of the filter is communicated with the vapor discharge chamber via a communication passage.
Further, in accordance with a third aspect of the present invention, in addition to the first aspect mentioned above, the vapor separator is characterized in that the filter is separated into a downstream chamber in which a fuel insertion port is open upward, a vapor discharge recess portion separated from the downstream chamber including the fuel insertion port and open upward and an upstream chamber recess portion open downward by a filtrating member arranged in a middle portion, and provided with a support leg portion open to the vapor discharge recess portion and supported to an outer periphery of the high pressure fuel pump so as to extend upward, the fuel suction passage of the high pressure fuel pump is inserted within the fuel insertion port, the vapor discharge chamber is formed by the bottom portion of the high pressure fuel pump and the vapor discharge recess portion, the support leg portion is brought into contact with and arranged on the outer periphery of the high pressure fuel pump, the upstream chamber of the filter is formed by the upstream chamber recess portion of the filter and the bottom portion of the fuel pump receiving case by the high pressure fuel pump provided with the filter being arranged toward the bottom portion of the fuel pump receiving case in a contact manner, an annular chamber connected to the vapor discharge chamber is formed by the outer periphery of the high pressure fuel pump and the inner periphery of the fuel pump receiving case, and the annular chamber is open to the portion below and close to the fixed liquid surface of the vapor separator by the vapor discharge passage.
In accordance with the first aspect, the high pressure fuel pump is arranged within the fuel pump receiving case arranged outside the vapor separator. The filter is arranged in the bottom portion within the fuel pump receiving case, the fuel suction passage of the high pressure fuel pump is connected to and arranged in the downstream chamber of the filter, and the upstream chamber of the filter is connected to the portion below the fixed liquid surface of the vapor separator via the fuel inflow passage. The vapor discharge chamber separated from the downstream chamber of the filter is formed within the fuel pump receiving case, the vapor discharge port of the high pressure fuel pump is open to the vapor discharge chamber, the annular chamber formed by the outer periphery of the high pressure fuel pump and the inner periphery of the fuel pump receiving case is communicated with the vapor discharge chamber, and the annular chamber is communicated with the portion below and close to the fixed liquid surface of the vapor separator via the vapor discharge passage. The fuel stored within the vapor separator flows toward the downstream chamber from the upstream chamber of the filter via the fuel inflow passage, a clean fuel within the downstream chamber is sucked into the pump via the fuel suction passage so as to increase the pressure thereof when the high pressure fuel pump is driven, and the fuel having the high pressure is discharged via the fuel discharge passage. The bubbles generated in the high pressure fuel pump is discharged into the vapor discharge chamber via the vapor discharge port, and the bubbles are discharged into the fuel below and close to the fixed liquid surface of the vapor separator via the annular chamber and the vapor discharge passage.
In accordance with the second aspect, since the upstream chamber of the filter and the vapor discharge chamber are communicated by the communication passage, even when the bubbles generated in the fuel of the vapor separator flow into the upstream chamber of the filter from the fuel inflow passage, the bubbles flow into the vapor discharge chamber from the communication passage and next is again discharged into the vapor separator via the annular chamber and a vapor discharge passage.
In accordance with the third aspect, the filter is structured such that the downstream chamber in which the fuel insertion port is open above the filtration member, and the vapor discharge recess portion separated from the fuel insertion port and the downstream chamber is formed, the upstream chamber recess portion is formed below the filtration member, and the support leg portion is supported to the outer periphery of the high pressure fuel pump and open to the vapor discharge recess portion. The fuel suction passage of the high pressure fuel pump is inserted and arranged within the fuel insertion port connected to the downstream chamber of the filter by inserting and arranging the bottom portion of the high pressure fuel pump toward the downstream chamber of the filter, the vapor discharge chamber is formed by the bottom portion of the high pressure fuel pump and the vapor discharge recess portion, and the vapor discharge port of the high pressure fuel pump is open within the vapor discharge chamber. The high pressure fuel pump provided with the filter is received and arranged toward the bottom portion of the fuel pump receiving case, whereby the filter upstream chamber connected to the fuel inflow passage is formed by the upstream chamber recess portion of the filter and the bottom portion of the fuel pump receiving case, and the vapor discharge chamber is communicated with the annular chamber formed on the outer periphery of the high pressure fuel pump.